Sqlite is used and only implementation differs, as I know.
I assume next version would have better handling, if you
upgraded and experienced the same problem.
Regarding one file db, sqlite proved to be stable and works
fine on at least one gadget I own. No reason to change it
to something more advanced and much bigger.

Not really looking for something bigger/better. What I was wondering is if there is a way to restore the database to it's factory state. The reset currently leaves all kinds of bits and pieces behind. I don't want to be doing manual deletions and then vacuuming the database.

As an aside, since I picked up another Kobo as a birthday present for a friend who liked mine, I copied the database from that unit and saved it as a "factory clean" database copy.